The invention relates to a multipurpose tool for gripping cylindrical objects in a manufacturing environment, and more particularly to such a tool that can be used to grip cylindrical fasteners and drill bits.
Frequently, it is desired to grip a cylindrical object to impart rotation thereto, to prevent rotation thereof or to maintain the relative position of the gripping tool to the object. Most solutions rely upon a multi-component apparatus that utilizes radially moveable jaws, or constriction wrenches that employ a band or the like.
One area that relies upon a need to grip cylindrical objects relates to the field of locking collar fastener systems. These systems, sometimes called a frangible fastener or xe2x80x9cHI-LOKxe2x80x9d systems, are used in environments of high vibration, such as on aircraft, to join two parts together. A locking collar fastener system is used wherever a rivet can be used to join parts together. The frangible fastener system utilizes a first piece comprising a threaded shaft on one end and an exposed retaining ring at the other end. A passage is drilled through the parts to be fastened typically large sheets of metal such as aircraft surfaces and boats. The threaded shaft portion of the fastener is inserted through the aligned passages to the exposed retaining ring. Often the surface of the part to be fastened is indented at the hole consistent with the retaining ring to provide a flat outer surface at the area of the retainer ring. A matching threaded locking collar is hand rotated upon the threaded portion of the shaft, then controllably torqued with a wrench. The threaded locking collar joins to a wrenching ring by a notched neck, which shears from the collar at a predetermined torsional loading during the torquing. The threaded locking collar having an upset portion, usually a slightly elliptical shape, provides a frictional spring lock to prevent the locking collar from un-treading or loosening, even in environment of high vibration and stress. The collar remains locked to the fastener shaft even when the residual tension on the fastener is lost.
The removal of the HI LOK and other frangible fasteners without damage to the part attached often presents a challenging problem but is needed for many useful reasons. On the HI LOK type frangible fastener, an hexagonal opening at the end of the shaft of the locking collar fastener is sufficiently recessed in depth to receive a standard allen wench for the purpose of retaining the shaft in position with respect to the locking collar during removal.
The removal of the locked collar from the shaft is usually difficult, but necessary for repair and maintenance of the joined parts. To accomplish this, heretofore, drilling means such as a drill bit manual, electric or air-motor are used to drill out the center of the shaft portion or a cutting means such as a hack-saw is used to cut the collar. In either case, this activity weakens the fastener. Then the parts of the collar are pried, chiseled or twisted off to expose the shaft portion of the fastener within the passage. Then a knock-out pin is used to force the shaft from the passage. The problem with this method is the time it takes to drill or cut and manipulate the collar in order to expose then remove the shaft from the passage. Furthermore, scars from the removal operations and consequential weakening to the parts surrounding the passage may create problems in refastening the parts using the same passage.
Ongoing efforts have been made to improve the means to remove these types of fasteners without causing damage. Such efforts have been addressed both to the general object of improving the manner of removal of the frangible fasteners as well as the speed that these fasteners may be removed without damage to the parts fastened. Because the frangible fasteners are designed to hold parts together in environments involving extreme stress and vibration, no universally adaptable tool was known to address the removal of frangible fasteners without encountering the difficulties noted above.
In addition to the foregoing, another area wherein gripping of a cylindrical object is desired relates to drill stops. Conventional technologies have traditionally relied upon a collar sized to fit about the drill bit and held in place by a set screw at a precise location on the drill bit. Because the act of drilling involves the use of substantially axial pressure on the drill bit to advance the same through the material being drilled, such stops often encounter impact forces when the drill bit passes through the material. The result is that the stop stops forward momentum. However, because the stop has only one point of contact, i.e., the set screw, these stops are often displaced from their precise location on the bit. Efforts to overcome this consequence have relied upon progressively slowing the forward momentum by using a compression spring located between the stop and the material. This solution, however, does not eliminate the problem entirely. Moreover, the set screw may not reside on a land, or may otherwise be damaged by the bit, or damage the bit.
The invention is directed in part to a tool for grasping cylindrical objects within a given diameter range, which have an exposed end. The tool comprises an outer cylinder, an inner cylinder, and a collet, which interacts between the two cylinders whereby the internal diameter of the collet is affected. The outer cylinder has a first end, a second end, an outer surface and an inner surface wherein the inner surface includes a threaded portion and a frusto-conical portion. The inner cylinder havs a first end, a second end, an outer surface and an inner surface wherein the outer surface includes a threaded portion adapted to engage the outer cylinder threaded portion. The collet is sized to fit within the outer cylinder and has a first end, a second end, an outer surface and an inner surface wherein the outer surface has a generally frusto-conical profile generally complementary to the outer cylinder frusto-conical portion. The collet further defines a gap extending from the outer surface to the inner surface, and from the first end to the second end. When presented with a radially compressive force, the gap dimension of the collet is modified thereby causing radial constriction of the collet around the cylindrical object when placed within the boundaries of the collet inner surface.
In a preferred embodiment, the inner cylinder threaded portion engages the outer cylinder threaded portion to enable the inner cylinder to occupy the inner volume defined by the outer cylinder. When the collet is placed in the internal boundaries of the outer cylinder, the outer surface of the collet, which is preferably a frusto-conical or tapered form, contacts the frusto-conical or tapered portion of the outer cylinder; an upper rim portion of the collet then contacts the second end or lower area of the inner cylinder. As the inner cylinder is rotated so as to progressively occupy the inner volume defined by the outer cylinder, the collet is urged towards the reduced diameter portion of the outer cylinder, thereby subjecting the collet to radial compression. In turn, this radial compression will cause the collet to grip any cylindrical object placed therein.
Depending upon application, the basic tool can be adapted to serve numerous functions. As previously described, the tool can be used to assist in the removal of frangible fasteners, or can be used as a drill stop. If a drill stop is desired, a preferred embodiment further comprises an end stop that is rotationally mounted to the second or lower end of the outer cylinder so that any contacted material encountered during drilling operations will not be subject to rotational abrasion. Advantageously, the collet provides nearly uniform radial compression over the entire surface contacting with the bit.